Measuring Technique for Reducing the Number of Voltage Sensors in a Modular Multilevel Converter

Summary of the technology

Voltage Sensors in a Modular Multilevel Converter

Universitat Politècnica de Catalunya - UPC
Universitat Politècnica de Catalunya - UPC

The Challenge

The operation of the MMC requires the use of a voltage balancing algorithm, which selects the SMs to be activated in order to maintain the SM capacitor voltages as close as possible to their reference value. This algorithm needs to know the values of all the SM capacitor voltages, which are usually obtained by direct measurement. In real applications of the MMC, the number of SMs per arm can reach to hundreds, requiring a large number of voltage sensors with their associated acquisition and processing circuitry. This compromises reliability of the MMC, besides complicating its implementation and control.

The Technology

The proposed system determines the SM capacitor voltages by using a minimum number of two voltage sensors per arm. Each voltage sensor is connected to the output of a set of series-connected SMs within each arm, acquiring the voltage measurement only when one SM of the set is activated. The acquired value corresponds to the capacitor voltage of the activated SM minus some voltage drops in the semiconductors, which can be easily estimated. Since the measurements of all the capacitor voltages are not always available, they are estimated by a mathematical model. In this mathematical model the capacitor voltage values are updated whenever there is a new measurement available. In order to ensure periodic update of each of the estimated capacitor voltages, an algorithm that enforces measurement of each capacitor voltage is proposed. Moreover, the reliability of this measuring technique can be improved by adding some redundant voltage sensors.

Current stage of development

Experimental prototype and tests passed.

Applications and Target Market

  • Measurement and data acquisition systems in MMCs.
  • Fault-tolerance improvements of MMCs.
  • MMC manufacturers.

Innovative advantages

  • Reducing the number of voltages sensors needed to measure the SM capacitor voltages in the MMC, hence reducing the direct and indirect costs.
  • Reliability improvement by adding redundant voltage sensors.
  • Highly tolerant to switching noise, as measures are taken between commutations.

Intellectual property status

  • Granted Patent
  • Patent application number :-

Related Keywords

  • Signal Processing
  • Electrical Engineering and Technology / Electrical Equipment
  • Renewable Sources of Energy
  • Energy efficiency
  • Power Electronics

About Universitat Politècnica de Catalunya - UPC

The Universitat Politècnica de Catalunya - BarcelonaTech is a public institution dedicated to higher education and research in the fields of engineering, architecture and science, which contributes its knowledge and expertise in order to increase scientific output, transfer its results to society and provide a network of scientific and technical state-of-the-art facilities and technology valorization services that place us at the leading edge of innovation and economic development.

The UPC has established itself as a driver of innovation and is the technology partner of choice for companies and organizations with which it develops projects and builds partnerships. A role borne out by the numerous agreements and research projects that have been set in motion by groups, organizations and laboratories; the creation of new technology-based companies; the generation and exploitation of patents, and the scientific and technical services UPC makes available to its environment in order to generate progress and employment.

The Technology Transfer Office (SGI) is responsible of Designing, coordinating and implementing research valorisation strategies, carrying out the protection policy of the research results, marketing these results through license contracts and designing and setting up the University's enterprise creation model in order to transfer the results of the research to the market, protect and commercialize these results, promote the culture of entrepreneurship and innovation, and create technology-based companies within the UPC environment.

Universitat Politècnica de Catalunya - UPC

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